Last week, longtime independent Vermont Senator and avowed socialist Bernie Sanders announced that he will run for the presidency in 2016.

Sanders’s announcement excited liberal activists wary of another centrist Clinton presidency but puzzled most political pundits, who see no chance for a socialist candidate to do much of anything other than draw a few votes away from the eventual Democratic candidate.

Yet American history is rife with such quixotic presidential campaigns, and they can be divided into a few distinct types that can each shed light on Sanders’ goals for his candidacy.

There are those campaigns driven by a consistent and radical ideology, such as that of Socialist candidate Eugene Debs; those in which a Washington insider mounts a third-party challenge to the two-party status quo, such as Teddy Roosevelt’s 1912 effort; those in which a true outsider takes on the political system as such, including Ross Perot’s and Ralph Nader’s campaigns; and, most saliently for Sanders, those in which a candidacy can become a symbol of American ideals far beyond partisan politics, such as Shirley Chisholm in 1972 and Jesse Jackson in 1988.

Debs Ran—Even From Jail

Most obviously similar to Sanders, of course, are the five presidential campaigns of labor activist Debs.

Like Sanders an avowed socialist, Debs ran for president in 1900 on the Social Democratic ticket and in 1904, 1908, 1912 and 1920 as a Socialist. These multiple campaigns indicated not a refusal to face reality so much as a genuine, consistent groundswell of support for Debs as an alternative candidate—indeed, he received the most votes in his final 1920 run, despite at the time being in prison for violating the 1917 Espionage Act.

Like Debs before him, Sanders will no doubt receive substantial support from Americans who feel disconnected from our centrist political parties and narratives.

Whereas Debs never held elected office, however, Sanders has been a member of Congress—first as a Congressman, then a Senator—or more than 25 years before embarking on this first presidential run. As such, he also resembles another insider third party candidate, Teddy Roosevelt, who having served most of two prior terms as a Republican president (from William McKinley’s 1901 assassination through William Howard Taft’s 1909 inauguration), subsequently decided to oppose Taft on the ticket of the Progressive Bull Moose Party in the 1912 election.

Roosevelt Challenged the Two-Party System

Roosevelt saw the Republican Party as having abandoned the Progressive policies for which he had fought, and believed an outsider run was necessary to bring such a platform back into the national conversation—a description that seems to fit Sanders’s perspective on the Democratic Party in 2015 quite well.

As a very popular ex-president, however, one bound for Mount Rushmore no less, Roosevelt stood a far better chance of competing seriously for the presidency than does Sanders.

As a result, and in his perspective as a critic of virtually everything about mainstream Washington, Sanders could also be compared to truly symbolic outsider presidential candidates, the two most famous of whom have both run in the last couple decades: Ross Perot in 1992 and Ralph Nader in 2000.

Perot and Nader weren’t exactly running to compete for the presidency, nor were they driven by an ideological agenda as overt and consistent as Debs’s Socialism. Instead, their goals could be described as both raising awareness of what they saw as our system’s fundamental flaws and helping Americans realize they don’t have to accept that status quo.

When Sanders claims that he is running to demonstrate that our contemporary economy is both “immoral” and “unsustainable,” he represents another such stringent critique of the current system.

Chisholm and Jackson’s Challenges

I would highlight one additional salient historical context for Sanders’s campaign, and it’s both the most unlikely and, to my mind, the most important: the presidential candidacies of Shirley Chisholm in 1972 and Jesse Jackson in 1988.

These two Civil Rights activists and leaders undoubtedly ran to draw attention to the specific issues of race, ethnicity and gender about which they cared so deeply and for which they fought so consistently.

Yet in so doing, they also did something else, something even more sweeping: they redefined, for a time, campaigns and the presidency and even politics themselves as far beyond partisanship.

For a time, both Chisholm and Jackson demonstrated how political campaigns and conversations can still embody our nation’s highest ideals and best qualities, can reflect the kinds of activism that from the abolitionists to the suffragettes to a bridge in Selma have stood and fought for those ideals.

Too often, it can seem that our politics have nothing to do with those battles. But campaigns like Chisholm’s and Jackson’s, and perhaps like Sanders’s, can bridge the gap and remind us all of what we fight for.

Whether these candidates could win the presidency was beside the point: Theirs were campaigns that changed the way we collectively imagine our national community, reminding us of voices and ideas that it’s all too easy to leave out of partisan politics.

Senator Bob Menendez said he was "disappointed, but not surprised, that the Trump administration has failed once again to prioritize our long-term national security interests or stand up for human rights."